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Study Guide: Chemistry of Life (Chapters 3-5) – General Biology

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  • 30 multiple choice

  • 2 free response questions (FRQ)

Chemistry of Life: Study Notes

Chapter 3: Water and Its Properties

Water is essential for life due to its unique chemical and physical properties. Understanding water's structure and function is fundamental in biology.

  • Structure and Function of Water: Water (H2O) is a polar molecule with a bent shape, resulting in partial positive and negative charges on opposite ends. This allows water to form hydrogen bonds with other molecules.

  • Importance of Hydrogen Bonding: Hydrogen bonds are weak attractions between the hydrogen atom of one water molecule and the oxygen atom of another. These bonds are responsible for water's high cohesion, adhesion, surface tension, and its ability to moderate temperature.

  • Polarity of Water: The polarity of water enables it to dissolve many substances, making it an excellent solvent for biological reactions.

  • Role of pH and Buffers in Cells: pH measures the concentration of hydrogen ions () in a solution. Buffers are substances that minimize changes in pH by accepting or donating hydrogen ions, helping maintain homeostasis in cells.

Example: Water's high specific heat helps organisms maintain stable internal temperatures.

Chapter 4: Carbon and Functional Groups

Carbon's versatility allows it to form a variety of complex molecules essential for life. Functional groups attached to carbon skeletons determine the properties and functions of organic molecules.

  • Seven Common Functional Groups:

    • Hydroxyl (–OH)

    • Carbonyl (–C=O)

    • Carboxyl (–COOH)

    • Amino (–NH2)

    • Sulfhydryl (–SH)

    • Phosphate (–PO42−)

    • Methyl (–CH3)

  • Structural Isomers, Cis-Trans Isomers, and Enantiomers:

    • Structural isomers differ in the covalent arrangement of atoms.

    • Cis-trans (geometric) isomers differ in spatial arrangement around a double bond.

    • Enantiomers are mirror images of each other and differ in shape due to the presence of an asymmetric carbon.

Example: The amino acid alanine exists as two enantiomers, only one of which is used in proteins.

Chapter 5: Macromolecules

Macromolecules are large, complex molecules essential for life, including carbohydrates, lipids, proteins, and nucleic acids. Each type has unique structures and functions.

  • Structure and Function of Macromolecules:

    • Carbohydrates: Serve as energy sources and structural materials. Monomers are monosaccharides (e.g., glucose).

    • Lipids: Include fats, oils, and steroids. They are hydrophobic and function in energy storage, insulation, and cell membrane structure.

    • Proteins: Polymers of amino acids with diverse functions including catalysis (enzymes), structure, and transport.

    • Nucleic Acids: DNA and RNA store and transmit genetic information. Monomers are nucleotides.

  • Common Atoms in Macromolecules: Carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur are commonly found in biological macromolecules.

  • Synthesis and Hydrolysis: Monomers are joined by dehydration synthesis (removal of water) and broken down by hydrolysis (addition of water).

  • Relationship Among DNA, Protein, and Enzyme: DNA encodes the instructions for protein synthesis. Proteins can function as enzymes, which catalyze biochemical reactions.

  • Mutations: Changes in the DNA sequence that can affect protein structure and function.

  • Levels of Protein Structure:

    1. Primary: Sequence of amino acids.

    2. Secondary: Local folding (α-helix, β-sheet) stabilized by hydrogen bonds.

    3. Tertiary: Overall 3D shape due to interactions among R groups.

    4. Quaternary: Association of multiple polypeptide chains.

  • Protein Folding: Proper folding is essential for function; misfolding can lead to diseases.

  • Structure of Amino Acids: Amino acids have a central carbon, amino group, carboxyl group, hydrogen atom, and R group (side chain). They are classified based on the properties of their R groups (e.g., polar, nonpolar, acidic, basic).

  • Structure of DNA and RNA:

    • DNA: Double helix with complementary base pairing (A-T, G-C).

    • RNA: Usually single-stranded, with uracil (U) instead of thymine (T).

Example: Hemoglobin is a protein with quaternary structure, composed of four polypeptide subunits.

FRQ Preparation

  • Graphing Guidelines: Understand how to construct and interpret scientific graphs, including labeling axes and identifying trends.

  • SEMs and Statistical Differences: Standard Error of the Mean (SEM) quantifies the precision of the sample mean estimate. Statistical differences in data sets can be assessed using SEM and other statistical tests.

Example: If error bars (representing SEM) on two data sets do not overlap, the difference is likely statistically significant.

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